I cannot recall any references from the literature concerning this. The
1993 study mentioned is the only reference of which I am aware.
The desirability of removal of the blood is however well established.
For most perfusion techniques the fixative is preceded by a saline or
buffer wash to remove excess blood and to prevent smaller vesels being
obstructed by blood being fixed in situ. The major advantage of
perfusion is not only the rapid delivery of fixative to individual cells
with a consequent rapid killing time, but the initial hardening of the
tissue which limits subsequent mechanical damage.
The major problem with fixation is control of the perfusion pressure and
opening of vessels which,  under normal circumstances are closed.
Additionally, some structures such as Schlemm's canal have been reported
to be decreased in size even when using physiologic intraocular
pressures.
Hope this is of use to you.
Barry